The present invention relates to a powered screening apparatus, and more particularly, to a vibrating screen used to separate and sort multiple size solids and particulates.
Vibrating screen arrangements have been in use for many years in gravel and rock quarrying for screening and/or for dewatering wet material. Generally, the arrangements comprise a working member supported on a frame and an exciter arranged to impart vibrating motion to the member. The working member is fitted with a screen deck with a conventionally rigid aperture element which may be made up of a plurality of screening panels.
Despite the fact that the working member is vibrated in use, blinding of the apertures in the screening material often occurs. When blinding occurs, separation of particulates become less uniform and less efficient. It is, therefore, an object of this invention to reduce blinding and improve efficiency.
Vibrating screen decks have also been widely in use in the past for separating particulates of various sizes and composition. Such screening decks typically comprise a rectangular frame suspended in operation with screen cloth mounted within the frame from which the materials are separated. The frame and screen in such decks are suspended at an angle. The entire frame is vibrated, thus imparting vibration to the machine which in turn causes the solids to move down the screen. As the materials move down the vibrating screen, the solids of smaller mesh size pass through the screen with larger solids discharged from the lower end of the screen.
One disadvantage of such prior screening devices is imparting vibrating motion to the entire system without a corresponding reduction in the blinding. Another disadvantage of the prior screening devices is that they require sufficient power to throw or move the solids along the vibrating screen. Still another disadvantage is that prior decks have to be built with heavier structural members to withstand the throwing of material and the increased power. Since prior screening devices are much heavier, structures to support them have to be much heavier and are more costly to construct. Another disadvantage is that prior screening devices have to be built substantially larger with greater screening area to produce the same amount of separated material as the present invention. Accordingly, it is an object of this invention to reduce the size and weight of the screening device needed to produce equivalent qualities of separated material. Prior screening devices are less inclined to enhance the separating efficiency of the device. The present device may be mounted at steeper angles and still maintain its efficiency. Gravity assists the movement of the material over the screen, which in turn requires less power to activate the present device. Decks of this size can typically employ motors of forty horsepower (40 hp) or more. Accordingly, it is an object of this invention to provide a device which is less costly to operate. Another disadvantage of such prior decks is the susceptibility of frequent maintenance because the vibration is imparted to the entire deck for sustained lengths of time. It is, therefore, an object of this invention to reduce maintenance caused by vibration.
Other screening apparatus have been developed which attempt to reduce the substantial energy requirement required in such devices and increase the frequency at which the screening surface vibrates. In these apparatus, a plurality of smaller vibrator motors have been employed which are coupled to vibrator shafts extending beneath the screen material at various locations spaced along the length of the screen. The vibrator shafts are coupled by relatively complex linkages to the vibrator motor on the exterior of the frame of the deck. A plurality of vibrator shafts or arms are positioned on the shaft which move eccentrically to vibrator screen from beneath. This particular vibrator arrangement in such decks necessitates relatively complex linkages and causes localized tapping of screen both of which result in concentrated wear. Such prior screening decks require frequent adjustment to keep the screen in contact with the vibrators. Such prior screening decks are also susceptible to frequent blinding. Such prior screening decks require the vibrators to run at relatively high rotating speeds (4,000 rpm to 45,000 rpm) to achieve the desired frequency. The high rotating speed decreases the life of bearings which increases maintenance or operating costs. In such prior screens, the screen is vibrated once per revolution. The present invention vibrates the screen twice per revolution, which increases screening efficiency. It is, therefore, an object of this invention to reduce the necessity for frequent adjustment, reduce operating costs, and increase the efficiency of the screening deck.